WO2013015210A1 - ポリアクリロニトリル系共重合体、炭素繊維用ポリアクリロニトリル系前駆体繊維、炭素繊維束、耐炎化繊維束の製造方法、および炭素繊維束の製造方法 - Google Patents
ポリアクリロニトリル系共重合体、炭素繊維用ポリアクリロニトリル系前駆体繊維、炭素繊維束、耐炎化繊維束の製造方法、および炭素繊維束の製造方法 Download PDFInfo
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/42—Nitriles
- C08F220/44—Acrylonitrile
- C08F220/48—Acrylonitrile with nitrogen-containing monomers
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
- D01D5/00—Formation of filaments, threads, or the like
- D01D5/253—Formation of filaments, threads, or the like with a non-circular cross section; Spinnerette packs therefor
-
- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
- D01F6/28—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F6/38—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolymers obtained by reactions only involving carbon-to-carbon unsaturated bonds comprising unsaturated nitriles as the major constituent
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- D—TEXTILES; PAPER
- D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
- D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
- D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material
- D01F9/12—Carbon filaments; Apparatus specially adapted for the manufacture thereof
- D01F9/14—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments
- D01F9/20—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products
- D01F9/21—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
- D01F9/22—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles
- D01F9/225—Carbon filaments; Apparatus specially adapted for the manufacture thereof by decomposition of organic filaments from polyaddition, polycondensation or polymerisation products from macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds from polyacrylonitriles from stabilised polyacrylonitriles
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/04—Acids; Metal salts or ammonium salts thereof
- C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/10—Esters
- C08F220/20—Esters of polyhydric alcohols or phenols, e.g. 2-hydroxyethyl (meth)acrylate or glycerol mono-(meth)acrylate
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
- C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
- C08F220/52—Amides or imides
- C08F220/54—Amides, e.g. N,N-dimethylacrylamide or N-isopropylacrylamide
- C08F220/56—Acrylamide; Methacrylamide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
- Y10T428/2913—Rod, strand, filament or fiber
- Y10T428/2918—Rod, strand, filament or fiber including free carbon or carbide or therewith [not as steel]
Definitions
- the present invention relates to a polyacrylonitrile-based copolymer, a polyacrylonitrile-based precursor fiber for carbon fibers, a carbon fiber bundle, a method for producing a flame-resistant fiber bundle, and a method for producing a carbon fiber bundle.
- Patent Document 1 uses a carbon fiber precursor fiber bundle having a high roundness and a large single fiber fineness to suppress burning spots during the flameproofing treatment, and the total fineness is In spite of its large size, it has proposed a technique for obtaining a carbon fiber bundle that has few entanglements between single fibers, is excellent in spreadability, and is also excellent in productivity.
- Patent Document 2 proposes a polymer that does not require a flameproofing process. Further, Patent Documents 3 and 4 improve the oxygen permeability of the carbon fiber precursor fiber by using a monomer having a bulky side chain as a copolymer component of the copolymer, thereby increasing the oxygen concentration in the flameproof fiber. A technique for uniformly controlling the distribution and improving the tensile strength and tensile modulus of the resulting carbon fiber has been proposed.
- Patent Document 5 discloses that polyacrylonitrile (PAN) -based carbon fiber precursor fibers are made flameproof while allowing heated air to pass through the yarn bundle on a mesh-like roller. It proposes a technology that suppresses heat storage.
- PAN polyacrylonitrile
- Patent Document 6 dramatically improves the thermal stability when the spinning dope is held at a high temperature of about 80 ° C. by esterifying methacrylic acid, which is a component for promoting the flame resistance reaction of the polymer.
- JP 2008-202207 A Japanese Patent Laid-Open No. 1-132832 Japanese Patent Laid-Open No. 2-84505 JP 2006-257580 A Japanese Patent Laid-Open No. 2-6625 JP 2007-204880 A
- the strength of the carbon fiber of Patent Document 2 may be significantly lower than that using PAN or pitch as a raw material, and may not meet market demands.
- Patent Documents 3 and 4 improve the permeability of oxygen into the fiber, further improvement has been required for cost reduction by shortening the flameproofing process.
- the precursor fiber bundle cannot maintain sufficient denseness or homogeneity to ensure the performance of the carbon fiber. was there.
- the present invention relates to a polyacrylonitrile-based precursor fiber for carbon fibers having a high single fiber fineness, which has high thermal stability of the spinning dope and excellent productivity, and a polyacrylonitrile-based copolymer suitable for the production of this precursor fiber.
- the purpose is to provide.
- the present invention also provides a high-quality carbon fiber bundle having a large single fiber fineness and excellent productivity, a method for producing the same, and a method for producing a flame-resistant fiber bundle suitable for producing the carbon fiber bundle. For other purposes.
- the first polyacrylonitrile-based copolymer of the present invention has an acrylonitrile unit of 93.0 mol% to 99.4 mol%, a (meth) acrylamide unit of 0.5 mol% to 4.0 mol%, A (meth) acrylamide derivative unit comprising an unsaturated carboxylic acid hydroxyalkyl unit of 0.1 mol% to 3.0 mol%, wherein the (meth) acrylamide unit is a (meth) acrylamide unit and a molecular weight of 105 or less. It is characterized by being either or both of these.
- the second polyacrylonitrile copolymer of the present invention comprises 93.0 mol% or more and 98.7 mol% or less of acrylonitrile units, 1.0 mol% or more and 4.0 mol% or less of (meth) acrylamide units, A (meth) acrylamide derivative unit comprising an unsaturated carboxylic acid hydroxyalkyl unit of 0.3 mol% to 3.0 mol%, wherein the (meth) acrylamide unit is a (meth) acrylamide unit and a molecular weight is 105 or less. It is characterized by being either or both of these.
- the unsaturated carboxylic acid hydroxyalkyl unit is preferably either one or both of a hydroxyalkyl methacrylate unit and a hydroxyalkyl acrylate unit.
- the polyacrylonitrile-based precursor fiber for carbon fiber of the present invention is characterized by comprising the first or second polyacrylonitrile-based copolymer. Further, the polyacrylonitrile-based precursor fiber for carbon fiber of the present invention preferably has a single fiber fineness of 1.5 dtex or more and 3.0 dtex or less.
- the method for producing a flame-resistant fiber bundle according to the present invention includes a precursor fiber bundle composed of the polyacrylonitrile-based precursor fiber for carbon fiber, in an oxidizing atmosphere at a temperature of 220 ° C. to 300 ° C. for 90 minutes or less. by heating at the time, the fiber density and obtaining the flame-resistant fiber bundle 1.35 g / cm 3 or more 1.43 g / cm 3 or less.
- the flame resistant fiber bundle obtained by the method for producing a flame resistant fiber bundle is heated in an inert gas at a temperature of 800 ° C. or higher and 2000 ° C. or lower to obtain a carbon fiber bundle. It is characterized by that.
- the carbon fiber bundle of the present invention is obtained by firing a precursor fiber bundle composed of the polyacrylonitrile-based precursor fiber for carbon fiber, and has a maximum single fiber diameter of 8 ⁇ m to 20 ⁇ m.
- the maximum diameter of the single fiber is the maximum of the distance between two points on the outer periphery of the cross section when a cross section perpendicular to the fiber axis of the single fiber is observed with a scanning electron microscope (SEM). Mean value.
- the polyacrylonitrile-based precursor fiber for carbon fiber having a high single fiber fineness, which has high thermal stability of the spinning dope and excellent productivity, and a polyacrylonitrile-based copolymer suitable for the production of this precursor fiber are provided.
- a polymer is provided.
- the content of acrylonitrile units in the polyacrylonitrile copolymer of the present invention (hereinafter sometimes simply referred to as a copolymer) is 93.0 mol% or more and 99.4 mol% or less. If it is 93.0 mol% or more, it is not affected by the decrease in carbon fiber performance due to the decrease in the copolymerization rate of acrylonitrile units.
- the upper limit of 99.4 mol% is defined by the necessary amounts of copolymerization components ((meth) acrylamide, (meth) acrylamide derivative and unsaturated hydroxycarboxylic acid hydroxyalkyl having a molecular weight of 105 or less) described later. is there.
- the upper limit of content of the acrylonitrile unit in a copolymer is 98.7 mol% or less, and a minimum is 95.0 mol% or more from a viewpoint of performance maintenance of the carbon fiber obtained. preferable.
- the total content of (meth) acrylamide units in the copolymer is 0.5 mol% or more and 4.0 mol% or less.
- (meth) acrylamide means either one or both of methacrylamide and acrylamide.
- the (meth) acrylamide unit means either one or both of a (meth) acrylamide unit and a (meth) acrylamide derivative unit having a molecular weight of 105 or less.
- this molecular weight means the molecular weight of the (meth) acrylamide derivative which forms a (meth) acrylamide derivative unit.
- This (meth) acrylamide unit is highly random copolymerizable with acrylonitrile, and it is thought that a ring structure is formed in a form very similar to acrylonitrile by heat treatment. Are very few. Furthermore, the molecular weight of the (meth) acrylamide unit used in the present invention can be made smaller than that of the unsaturated carboxylic acid hydroxyalkyl unit described later, so even if it is contained in a large amount, the mole of the acrylonitrile unit in the copolymer. The effect on the content is small, and the solubility in a solvent can be improved while suppressing a decrease in carbon fiber performance.
- the amide group of the (meth) acrylamide unit is a hydrophilic group, in the process of spinning the polyacrylonitrile copolymer (spinning process), the diffusion rate of water into the fiber during coagulation is moderated.
- a dense or homogeneous carbon fiber precursor fiber bundle (hereinafter sometimes referred to as a precursor fiber bundle) can be obtained.
- the content of the (meth) acrylamide unit in the copolymer is 4.0 mol% or less, it is easy to suppress the deterioration of the carbon fiber performance as described above. Further, if the content of the (meth) acrylamide unit in the copolymer is 0.5 mol% or more, the content of the acrylonitrile unit is not too high, and the solubility in the solvent when obtaining the spinning dope is increased. It becomes easy to suppress the decrease and the decrease in the denseness of the precursor bundle necessary for maintaining the performance of the obtained carbon fiber bundle.
- the content of the (meth) acrylamide unit in the copolymer is preferably 1.0 mol% or more from the viewpoint of the solubility and hydrophilicity of the copolymer, and the content of the acrylonitrile unit in the copolymer Is preferably 2.0 mol% or less from the viewpoint of maintaining a high value.
- the (meth) acrylamide derivative having a molecular weight of 105 or less has only to have a (meth) acrylamide structure in the molecular structure.
- a (meth) acrylamide structure for example, N-methylacrylamide, N-methylmethacrylamide, N, N-dimethylacrylamide, And N- (hydroxymethyl) acrylamide.
- the molecular weight of the (meth) acrylamide derivative is preferably smaller than the molecular weight of the unsaturated hydroxyalkyl hydroxy acid used in the copolymer, and is 105 or less from the viewpoint of carbon fiber performance.
- (meth) acrylamide derivatives) may be used alone or in combination. Furthermore, you may use together (meth) acrylamide and a (meth) acrylamide derivative. In addition, when using these together, if the total amount of the (meth) acrylamide type unit in a copolymer will be 0.5 mol% or more and 4.0 mol% or less, these compounding ratios can set freely. I can do it.
- acrylamide has a small molecular weight, so that even if it is introduced in a large amount into the copolymer, the mass ratio of acrylonitrile in the copolymer can be kept high, and it can be easily obtained industrially.
- the content of unsaturated hydroxyalkyl units in the copolymer is from 0.1 mol% to 3.0 mol% in total.
- unsaturated carboxylic acid hydroxyalkyl include, for example, hydroxyalkyl methacrylate, hydroxyalkyl acrylate, hydroxyalkyl 3-butenoate, hydroxyalkyl 2-methyl 3-butenoate, hydroxyalkyl 4-pentenoate, 2-methyl 4- Examples thereof include hydroxyalkyl pentenoate. These may be used alone or in combination of two or more.
- the unsaturated carboxylate hydroxyalkyl is either hydroxyalkyl methacrylate or hydroxyalkyl acrylate. One or both are preferred.
- the number of carbon atoms of the hydroxyalkyl group in the unsaturated carboxylic acid hydroxyalkyl is preferably 2 or more from the viewpoint of ensuring oxygen diffusibility in the flameproofing treatment step, and 5 from the viewpoint of polymerizability to acrylonitrile and industrial availability.
- the alkyl in the hydroxyalkyl group may be linear or branched. Further, the hydroxy group in the unsaturated alkyl carboxylate may be one, or may be two or more.
- the carboxylic acid hydroxyalkyl group in the unsaturated carboxylic acid hydroxyalkyl unit is thermally decomposed into a carboxylic acid group at a high temperature of 240 ° C. or higher. If the content of the unsaturated carboxylic acid hydroxyalkyl unit in the copolymer is 0.1 mol% or more, the carboxylic acid hydroxyalkyl group in the unsaturated carboxylic acid hydroxyalkyl unit becomes a carboxylic acid group in the flameproofing step. A sufficient effect of accelerating the flameproofing reaction. On the other hand, if it is 3.0 mol% or less, runaway of the flameproofing reaction can be suppressed. Furthermore, the yield reduction accompanying thermal decomposition of the hydroxyalkyl group in the flameproofing step can be suppressed.
- the lower limit of the content of the unsaturated carboxylic acid hydroxyalkyl unit in the copolymer is preferably 0.3 mol% or more, more preferably 0.5 mol% or more in that a higher-performance carbon fiber bundle can be obtained.
- the upper limit of the content of the unsaturated carboxylic acid hydroxyalkyl unit is preferably 2.0 mol% or less in terms of suppressing a decrease in yield due to thermal decomposition of the hydroxyalkyl group in the flameproofing step. The mol% or less is more preferable.
- the hydroxyalkyl group of the carboxylic acid in the unsaturated carboxylic acid hydroxyalkyl is a relatively bulky functional group, and has the effect of improving oxygen permeability into the precursor fiber bundle in the flameproofing step.
- oxygen is sufficiently diffused to the inside of the single fiber even while the progress of the flameproofing reaction is suppressed, so that the precursor fiber bundle having a large single fiber fineness is flameproofed from a high temperature in a short time.
- the hydroxyalkyl carboxylate group in the unsaturated hydroxyalkylate is a hydrophilic group, the diffusion rate of water into the fiber during coagulation in the process of spinning the polyacrylonitrile copolymer (spinning process) And a dense or homogeneous precursor fiber can be obtained.
- hydroxyalkyl methacrylate As described above, in the present invention, it is preferable to use one or both of hydroxyalkyl methacrylate and hydroxyalkyl acrylate as the unsaturated carboxylic acid hydroxyalkyl.
- hydroxyalkyl methacrylate examples include 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate, and monoglyceryl methacrylate.
- hydroxyalkyl acrylate examples include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, monoglyceryl acrylate, and the like.
- hydroxyalkyl methacrylate and hydroxyalkyl acrylate may be used in combination.
- the content of the unsaturated carboxylic acid hydroxyalkyl units in the copolymer is 0.1 mol% or more in total. If it is 0 mol% or less, it can be freely selected.
- 2-Hydroxyethyl methacrylate and 2-hydroxyethyl acrylate have a hydroxyethyl group elimination temperature of 240 ° C. or higher in the flameproofing step, and are bulky enough to improve oxygen permeability.
- the decrease in mass when the hydroxyethyl group is eliminated is small and that it is easily industrially available, it is suitable as a constituent of the copolymer of the present invention.
- the molecular weight of the copolymer can be evaluated by the specific viscosity ⁇ sp calculated by the following formula (1).
- ⁇ sp ( ⁇ - ⁇ 0) / 5 ⁇ 0 ⁇ formula (1)
- ⁇ is the viscosity of a solution obtained by dissolving the copolymer in a predetermined solvent
- ⁇ 0 is the viscosity of this solvent.
- the viscosity of the solution is measured, for example, by dissolving 0.5 g of the copolymer in 100 ml of a solvent (for example, dimethylformamide) and measuring the obtained solution at 25 ° C. using an Ubbelohde viscometer. Can do.
- the ⁇ sp of the copolymer of the present invention is preferably 0.20 or more and 0.26 or less. If it is 0.20 or more, performance deterioration of the obtained carbon fiber can be easily suppressed, and if it is 0.26 or less, the viscosity of the obtained spinning dope becomes low and gelation is easily suppressed. I can do it. More specifically, if it is 0.26 or less, the solubility of the copolymer in the solvent at the time of adjusting the spinning stock solution can be easily maintained appropriately. When gelling at a low temperature, there remains no undissolved core copolymer, and gelation can be easily suppressed.
- the method for producing the copolymer is not particularly limited, and a known method such as solution polymerization or suspension polymerization can be employed.
- the polymerization initiator is not particularly limited, and an azo compound, an organic peroxide, or a redox catalyst such as persulfuric acid / sulfurous acid or ammonium salt of chloric acid / sulfurous acid can be used.
- each monomer, distilled water, ammonium persulfate, ammonium bisulfite and sulfuric acid are continuously supplied in a constant amount into an overflow type polymerization vessel, and stirring is continued while maintaining a constant temperature.
- the polymer slurry thus obtained can be washed and dried to obtain a copolymer.
- a carbon fiber bundle can be produced from the copolymer of the present invention by a method for producing a carbon fiber bundle having the following steps.
- a step of preparing a spinning dope by dissolving the copolymer in a solvent (2) A step of spinning the spinning dope to obtain a precursor fiber bundle.
- a step of heating (flameproofing) the precursor fiber bundle at 220 ° C. or more and 300 ° C. or less for 90 minutes or less in an oxidizing atmosphere.
- a carbon fiber bundle can be obtained by firing a precursor fiber bundle composed of precursor fibers made of the copolymer of the present invention.
- the firing is performed in a flameproofing process in which the precursor fiber bundle is heated in an oxidizing atmosphere (for example, air) of 220 ° C. or higher and 300 ° C. or lower and in an inert atmosphere of 800 ° C. or higher and 2000 ° C. or lower.
- an oxidizing atmosphere for example, air
- the maximum temperature in the inert gas is lower than the carbonization treatment temperature (see FIG.
- the pre-carbonization process which heats at 550 degreeC or more and less than 800 degreeC can also be performed (pre-carbonization process).
- the said baking can also consist of the said flame-proofing process, a pre-carbonization process, and a carbonization process.
- the spinning dope preferably has a copolymer concentration of a certain level or more in order to obtain a dense coagulated yarn and to have proper viscosity and fluidity.
- concentration of the copolymer in the spinning dope is preferably 15% by mass or more and 30% by mass or less, and more preferably 18% by mass or more and 25% by mass or less.
- the conventional spinning dope (a solution obtained by dissolving a conventional polyacrylonitrile-based copolymer in an organic or inorganic solvent) is likely to be gelled due to an increase in viscosity mainly due to two factors.
- the first is due to a cyclization condensation reaction between nitrile groups in the polyacrylonitrile copolymer. This is the same reaction as the flameproofing reaction, and is promoted by the carboxy group in the copolymer. Therefore, it is considered that gelation is more likely to occur when the spinning dope is held at a high temperature of about 80 ° C.
- the second is due to the intermolecular association of carboxy groups or hydroxy groups in the polyacrylonitrile polymer. This is more likely to occur when the molecular motion is smaller, so it is more likely to occur when the spinning stock solution is held at a low temperature of about 30 ° C. If there are undissolved copolymers in the spinning stock solution, they become the core. Therefore, it is considered that gelation easily occurs.
- Presence of undissolved materials and gels in the spinning dope may lead to troubles in the spinning process and may greatly affect the productivity of the precursor fibers. It is very important to obtain a spinning dope with reduced slag.
- the carboxy group in the copolymer is esterified with a hydroxyalkyl group, the cyclization condensation reaction of the nitrile group can be suppressed. Therefore, even if the spinning solution is held at a high temperature of about 80 ° C., gelation is extremely difficult to occur.
- the unsaturated carboxylate hydroxyalkyl group containing a hydroxyalkyl group has a large molecular weight. Therefore, when trying to secure the desired molar composition in order to maintain the solubility of the copolymer in a solvent properly, The content of unsaturated carboxylic acid hydroxyalkyl tends to be very large. For this reason, there was concern that the acrylonitrile content in the copolymer would be low and the yield of the carbon fiber finally obtained would be reduced.
- the stock solution stability of the spinning dope is preferably stable (not gelled) at 80 ° C. for 50 days or longer and at 30 ° C. for 30 days or longer. If it is stable for 50 days or more when held at 80 ° C. and stable for 30 days or more at 30 ° C., even if it is exposed to severe temperature changes in the production process of the carbon fiber precursor fiber bundle, It is considered that gelation does not affect the process.
- ⁇ Preparation of spinning dope (step 1)> The above copolymer is dissolved in a solvent to obtain a spinning dope.
- a solvent organic solvents such as dimethylacetamide, dimethylsulfoxide, dimethylformamide, and aqueous solutions of inorganic compounds such as zinc chloride and sodium thiocyanate can be used.
- An organic solvent is preferable in that the precursor fiber does not contain a metal and the process is simplified.
- dimethylacetamide is preferably used in that the coagulated yarn and wet heat drawn yarn are highly dense. .
- the carbon fiber precursor fiber bundle used in the present invention is composed of a polyacrylonitrile-based precursor fiber for carbon fibers made of the above copolymer.
- the single fiber fineness of the precursor fiber bundle is preferably 1.5 dtex or more and 3.0 dtex or less. If the single fiber fineness of the precursor fiber bundle is 1.5 dtex or more, the productivity of the precursor fiber bundle can be easily made sufficiently high. On the other hand, if the single fiber fineness of the precursor fiber bundle is 3.0 dtex or less, it can be easily prevented that the cross-sectional double structure becomes prominent in the flameproofing process, and the carbon fiber bundle of uniform quality can be stably stabilized. Can be produced.
- the single fiber fineness is more preferably 1.8 dtex or more and 2.8 dtex or less, and 2.0 dtex or more and 2.5 dtex or less. More preferably, it is as follows.
- the cross-sectional shape of the single fiber of the precursor fiber bundle used in the present invention preferably has a roundness of 0.90 or less. Moreover, it is preferable that a cross-sectional shape is an empty bean type. If the cross-sectional shape is an empty bean type with a roundness of 0.90 or less, it is possible to easily prevent insufficient diffusion of oxygen into the single fiber constituting the precursor fiber bundle during the flameproofing treatment, and a sufficient flameproofing reaction. Can be easily advanced. As a result, fluff in the carbonization step can be easily suppressed, good processability can be easily obtained, and the strength and elastic modulus of the obtained carbon fiber bundle can be easily maintained appropriately.
- the roundness in the cross-sectional shape of the single fiber constituting the precursor fiber bundle is preferably 0.75 or more, and more preferably 0.80 or more. If the roundness is 0.75 or more, it can be easily prevented that the fiber content in the production of the prepreg from the obtained carbon fiber bundle is lowered by making the cross-sectional shape very different, This fiber content can be easily increased. Furthermore, it can prevent easily that the mechanical characteristic of the composite material using this carbon fiber bundle falls.
- the distance from the inside to the surface of the fiber is shorter than the conventional one. For this reason, even if the single fiber fineness is relatively increased, the flameproofing treatment can be performed uniformly and high-performance carbon fibers are easily obtained.
- the roundness of the single fiber constituting the fiber bundle (for example, the precursor fiber bundle or the carbon fiber bundle) can be obtained by the following formula (2).
- S and L in Formula (2) are the cross-sectional area and circumference of a single fiber obtained by carrying out SEM observation and image analysis, respectively, of the cross section perpendicular
- vertical to the fiber axis of a single fiber. Roundness 4 ⁇ S / L 2 (2)
- the carbon fiber precursor fiber bundle used in the present invention can be produced by spinning the polyacrylonitrile-based copolymer described above by a known method. Hereinafter, the spinning method will be described.
- the spinning method a known method can be employed, and specific examples include a wet spinning method, a dry wet spinning method, a dry spinning method, and the like. Among these, the wet spinning method and the dry wet spinning method are preferably used from the viewpoint of spinning productivity and the strength development of carbon fiber.
- the coagulated yarn can be obtained by discharging and spinning the above spinning solution into a coagulation bath through a spinneret.
- a dimethylacetamide aqueous solution having a dimethylacetamide concentration of 30% by mass to 70% by mass and a temperature of 20 ° C to 50 ° C.
- the concentration is 30% by mass or more, the coagulation rate can be easily maintained within an appropriate range, and rapid shrinkage of the coagulated yarn can be easily prevented, and the yarn denseness can be easily maintained. Can do.
- the concentration is 70% by mass or less, the coagulation rate can be easily maintained in an appropriate range, and thus adhesion between single yarns of the obtained precursor fiber bundle can be easily suppressed.
- the concentration is more preferably 65% by mass or less from the viewpoint of further suppressing adhesion between single yarns.
- the concentration of the coagulation bath is set to 60% by mass or less from the viewpoint of setting the roundness in the cross-sectional shape of the single fiber to 0.90 or less. It is particularly preferable to do this.
- the temperature is 20 ° C. or higher, the coagulation tension can be easily maintained in an appropriate range, and the occurrence of single yarn breakage can be easily suppressed in the coagulation bath. Furthermore, the cooling operation of the coagulation bath can be simplified, capital investment and running cost can be easily suppressed, and the precursor fiber bundle can be easily produced at low cost. On the other hand, if the temperature is set to 50 ° C. or lower, a decrease in the strand strength of the carbon fiber bundle obtained by firing the precursor fiber bundle can be easily suppressed.
- the temperature of the aqueous dimethylacetamide solution used in the coagulation bath is more preferably 25 ° C. or more and 40 ° C.
- the temperature of the coagulation bath is 35 ° C. or less from the viewpoint of setting the roundness in the cross-sectional shape of the single fiber to 0.90 or less. It is particularly preferred.
- the properties of the coagulated yarn are extremely important, and it is preferable that the number of macrovoids is less than 1 in a 1 mm length of the coagulated yarn.
- the macro void is a general term for voids having a spherical shape, a spindle shape, or a cylindrical shape having a maximum diameter of 0.1 to several ⁇ m.
- the coagulated yarn produced from the copolymer of the present invention has few such macrovoids and is obtained by sufficiently uniform coagulation. If there are many macrovoids, the coagulated yarn is devitrified and becomes cloudy. However, the coagulated yarn according to the present invention is hardly devitrified and hardly clouded because there are almost no macrovoids.
- the presence or absence of macrovoids can be easily determined by observing the coagulated yarn directly with an optical microscope or by observing a cross section of the coagulated yarn with an appropriate method using an optical microscope.
- wet heat drawing can be performed on the obtained coagulated yarn.
- the orientation of the fiber can be further increased.
- the wet heat drawing is performed by drawing the coagulated yarn while being washed with water, or drawing in hot water. Drawing at the same time as washing with water is preferable from the viewpoint of simplification and efficiency of the spinning process, and drawing in hot water is preferable from the viewpoint of productivity.
- the stretching ratio in wet heat stretching is preferably 2.5 times or more, and more preferably 3.0 times or more. When it is 2.5 times or more, a sufficient effect of increasing the fiber orientation can be easily obtained.
- the upper limit of the draw ratio is not particularly limited, but is preferably 6.0 times or less from the viewpoint of the stability of the spinning process.
- a silicone oil to the fiber bundle that has been subjected to wet heat drawing.
- the silicon-based oil a general silicon-based oil such as an aminosilicon-based oil can be used.
- the silicon-based oil is preferably prepared and used at a concentration of 0.4% by mass or more and 1.5% by mass or less.
- concentration of the silicon-based oil agent is 0.4% by mass or more, it is possible to easily prevent the amount of the oil agent from adhering to the fiber bundle from being extremely reduced, and when it is 1.5% by mass or less, It can be easily prevented that the adhesion amount becomes very large.
- a more preferable range of the concentration of the silicone-based oil is 0.8% by mass or more and 1.5% by mass or less.
- the fiber bundle that has been subjected to the silicon oil addition process can be dried to obtain a dried fiber bundle (dried densified yarn), which is further subjected to steam drawing or dry heat drawing to obtain the dried fiber bundle.
- the bundle can also be stretched from 1.2 times to 4.0 times.
- a draw ratio is 1.3 times or more from a viewpoint of performance maintenance of a carbon fiber bundle.
- the moisture content of the fiber bundle that has been subjected to steam drawing or dry heat drawing can be adjusted with a touch roll as necessary, and then entangled by blowing air by a known method as necessary. Processing can be performed. From the above, a carbon fiber precursor fiber bundle can be obtained.
- a carbon fiber precursor fiber bundle can be obtained.
- by performing the entanglement process by providing the entanglement between the filaments of the carbon fiber precursor fiber bundle, it is possible to easily impart the convergence property, and it is easy to obtain the fiber bundle that maintains the form of one tow. Can get to.
- the fiber bundle can be made very difficult to disperse, and the firing process passability can be easily improved.
- the moisture content of the fiber bundle after adjusting the moisture content and before being entangled is preferably 15% by mass or less, more preferably 10% by mass or less, and further preferably 3%. It is from 5% by mass to 5% by mass. When the moisture content is 15% by mass or less, it is possible to easily prevent the single fibers from being easily entangled when the fiber bundle is entangled by blowing air.
- the degree of entanglement in the entangled carbon fiber precursor fiber bundle is preferably in the range of 5 to 20 pieces / m, more preferably in the range of 10 to 14 pieces / m.
- the degree of entanglement degree is 5 pieces / m or more, it is possible to easily obtain the effect of sufficiently improving the firing process passability by making the fiber bundle very difficult to disperse by providing the entanglement.
- the entanglement degree is 20 pieces / m or less, it is possible to easily prevent the resin impregnation property and the fiber opening property of the obtained carbon fiber bundle from being lowered.
- the degree of entanglement of the carbon fiber precursor fiber bundle is a parameter indicating how many times one single fiber in the fiber bundle is entangled with 1 m from other adjacent single fibers. This degree of entanglement can be measured by the hook drop method.
- the obtained precursor fiber bundle can be heated at a temperature of 220 ° C. or higher and 300 ° C. or lower for 90 minutes or less, that is, flameproofed, to obtain a flameproof fiber bundle in an oxidizing atmosphere.
- the flameproofing treatment temperature is set to a temperature of at least 240 ° C. or more during the flameproofing treatment.
- the oxidizing atmosphere may be an atmosphere containing an oxidizing substance such as nitrogen dioxide, sulfur dioxide, oxygen, and the like, for example, in the air.
- the oxidizing substance means a substance that causes combustion of an object by giving oxygen or a substance that can promote the combustion of the object.
- the treatment temperature is preferably 230 ° C or higher, more preferably 240 ° C or higher, and preferably 280 ° C or lower from the viewpoint of suppressing the runaway of the flameproofing reaction.
- the flameproofing treatment time is preferably 10 minutes or more and 90 minutes or less.
- the flameproofing treatment time is 10 minutes or longer, sufficient oxygen can be easily diffused into the single fibers constituting the precursor fiber bundle.
- the flameproofing treatment time is 90 minutes or less, it is possible to easily prevent the flameproofing treatment process from causing a loss of productivity in the production process of the carbon fiber bundle, and efficiently produce the carbon fiber bundle. It is possible.
- the flameproofing treatment time is more preferably 30 minutes or longer and 70 minutes or shorter.
- Density of oxidized fiber bundle obtained by the oxidization treatment is preferably not more than 1.35 g / cm 3 or more 1.43 g / cm 3. If it is 1.35 g / cm 3 or more, it is possible to easily produce a carbon fiber bundle without reducing the yield of the carbon fiber bundle. In general, the higher the flame resistant fiber density is, the higher the yield of the carbon fiber bundle obtained is, but it is known that the performance of the carbon fiber tends to decrease. If it is 1.43 g / cm 3 or less, it is possible to easily improve the yield of the obtained carbon fiber bundle while easily suppressing the deterioration of the performance of the carbon fiber.
- the density of the flameproof fiber bundle is more preferably 1.38 g / cm 3 or more and 1.41 g / cm 3 or less.
- the fiber density can be measured by a density gradient tube method based on JIS K7112.
- the flameproofing reaction is performed until the carboxylic acid hydroxyalkyl group (carboxylic acid ester group) in the unsaturated carboxylic acid hydroxyalkyl unit is thermally decomposed into a carboxylic acid group. Progress is suppressed.
- the carboxylic acid hydroxyalkyl group of the unsaturated carboxylic acid hydroxyalkyl unit is thermally decomposed at a high temperature of 240 ° C. or higher. When it becomes an acid group, it becomes possible to perform a flameproofing process quickly from a high temperature of 240 ° C. or higher.
- the flame retardant treatment of the precursor fiber bundle is started at a temperature at which the temperature of the fiber bundle is less than 240 ° C., and the oxygen is diffused into the single fiber (for example, 5 minutes to 20 minutes). After ensuring, flameproofing treatment can be performed at a temperature at which the temperature of the fiber bundle becomes 240 ° C. or higher.
- the carboxylic acid hydroxyalkyl group in the unsaturated carboxylic acid hydroxyalkyl unit is a relatively bulky functional group, and has the effect of improving oxygen permeability in the flameproofing step. Because of these effects, oxygen is efficiently diffused into the single fiber while the progress of the flameproofing reaction is suppressed, so that the flameproofing treatment of the precursor fiber bundle having a large single fiber fineness can be shortened from a high temperature. Even if it takes time, it is possible to obtain a flame-resistant fiber bundle in which the formation of a double cross-section structure is suppressed and the progress of flame resistance is uniform.
- a carbon fiber bundle can be produced by heating the obtained flameproofed fiber bundle in an inert gas at a temperature of 800 ° C. or higher and 2000 ° C. or lower, that is, carbonizing. Through the above steps 1 to 4, a carbon fiber bundle having a maximum single fiber diameter of 8 ⁇ m to 20 ⁇ m can be obtained.
- a graphite fiber bundle can also be produced by treating this carbon fiber bundle at a high temperature of 2500 ° C. or higher and 2800 ° C. or lower in an inert gas.
- An inert gas means a chemically stable gas that does not react with other substances, and specific examples include nitrogen, helium, and argon.
- the maximum diameter of the single fiber of the carbon fiber bundle is the longest line segment connecting two points on the outer periphery of the cross section when the cross section perpendicular to the fiber axis of the single fiber is observed with a scanning electron microscope (SEM). Let it be the maximum value of the distance between two points on the outer periphery of the line segment, that is, the cross section.
- the carbon fiber bundle is composed of thick single fibers having a maximum diameter of 8 ⁇ m or more
- the bending rigidity of each single fiber can be easily increased, and the fibers are less likely to be entangled due to disturbance during the manufacturing process.
- the number of entanglements in the yarn bundle can be easily reduced.
- the maximum diameter of the single fiber is more preferably 9 ⁇ m or more, and further preferably 10 ⁇ m or more.
- the contact portion between the single fibers inside the yarn bundle can be further reduced, and the frictional resistance between the single fibers can be easily reduced. Very good and excellent oxygen permeability.
- the maximum diameter of the single fiber is preferably 20 ⁇ m or less, more preferably 15 ⁇ m or less, and further preferably 14 ⁇ m or less.
- the maximum diameter of the single fiber of the carbon fiber bundle is preferably 8 ⁇ m or more and 20 ⁇ m or less, and particularly preferably 10 ⁇ m or more and 15 ⁇ m or less.
- the cross-sectional shape of the single fiber of the carbon fiber bundle obtained by the production method of the present invention can be expressed by the roundness of the cross section perpendicular to the fiber axis of the single fiber of the carbon fiber bundle.
- the roundness can be obtained by using the formula (2) similarly to the roundness of the precursor fiber bundle.
- the roundness of the cross-sectional shape of the single fiber of the carbon fiber bundle is preferably 0.90 or less. Furthermore, the cross-sectional shape is preferably an empty bean type. By making the cross-sectional shape a relatively simple shape of a round bean shape with a roundness of 0.90 or less, it is easy to pack single fibers densely, so the fiber content in the prepreg is easily improved. Therefore, it is possible to easily improve the mechanical properties of the composite material.
- the roundness of the single fibers constituting the carbon fiber bundle is more preferably 0.88 or less, and most preferably 0.86 or less so that the distance from the surface to the center of the single fibers is shortened.
- the roundness of the single fiber constituting the carbon fiber bundle is preferably 075 or more, and more preferably 0.80 or more. If the roundness is 0.75 or more, it is possible to easily prevent the fiber content from decreasing when the prepreg is produced by making the cross-sectional shape very different, and this fiber content can be easily reduced. Can be high. Furthermore, it can prevent easily that the mechanical characteristic of a composite material falls.
- a carbon fiber bundle having a relatively simple irregular cross section such as a flat shape or a three-leaf shape has a roundness of 0.75 or more and 0.90 or less.
- the single fibers are engaged with each other, and the spreadability is lowered.
- the single fibers rarely engage with each other, but compared with carbon fibers having roundness of 0.75 or more and 0.90 or less.
- the carbon fiber bundle obtained in the present invention preferably has a strand tensile strength of 3000 MPa or more and a strand elastic modulus of 230 GPa or more. If the strand tensile strength is 3000 MPa or more and the elastic modulus is 230 GPa or more, the strand tensile strength can be easily applied in most fields where carbon fibers are currently used, such as structural materials. From the same viewpoint, the strand tensile strength is more preferably 3500 MPa or more and the strand elastic modulus is more preferably 240 GPa or more, and particularly preferably the strand tensile strength is 4000 MPa or more and the strand elastic modulus is 245 GPa or more.
- the carbon fiber bundle obtained by this invention converges 12000 or more single fibers of the carbon fiber which has the said characteristic.
- the number of single fibers is also large, so that the productivity at the time of manufacture is greatly improved, and production at low cost becomes possible easily.
- the number of single fibers constituting the carbon fiber bundle is more preferably 24,000 or more, and further preferably 36000 or more.
- the number of single fibers (the number of filaments) constituting the carbon fiber bundle ) Is preferably 100,000 or less, more preferably 80000 or less, and even more preferably 60000 or less.
- the precursor fiber bundle and the flame-resistant fiber bundle are also configured within the above number.
- composition of polyacrylonitrile copolymer was measured by 1 H-NMR method as follows. Using dimethyl sulfoxide-d6 solvent as a solvent, the copolymer was dissolved and measured with an NMR measuring apparatus (trade name: GSZ-400, manufactured by JEOL Ltd.) under the conditions of a total number of 40 times and a measurement temperature of 120 ° C. The ratio of each monomer unit was determined from the integral ratio of chemical shift.
- Single fiber fineness of precursor fiber bundle means the weight per 10000 m of one fiber. More specifically, two bundles of precursor fibers are taken by 1 m, and the mass of each is divided by the number of filaments (that is, the number of holes in the die). After that, it was multiplied by 10,000, and the average value of the two values obtained was taken as the single fiber fineness of the precursor fiber bundle.
- the cross-sectional shape of the precursor fiber is an amount that does not cause compression deformation, and is an amount that does not blur because the sample moves at the time of photographing.
- An antistatic agent (trade name: Statiside, manufactured by Mitsui & Co., Plastics Co., Ltd.) was sprayed evenly for about 2 seconds onto the precursor fiber bundle held on the end portion of the tube.
- Statiside manufactured by Mitsui & Co., Plastics Co., Ltd.
- Pulling the cotton yarn passed through the tube the precursor fiber bundle to which the antistatic agent was adhered was introduced into the tube.
- the tube containing the precursor fiber bundle was cut to about 1 to 3 mm on a rubber plate using a razor.
- Fiber density of precursor fiber bundle and flameproof fiber bundle was measured by a density gradient tube method based on JIS K7112.
- Measurement of maximum diameter of single fiber cross section of carbon fiber bundle 20 pieces are arbitrarily selected from five photographs for each sample, but three or more single fiber sections are selected from one photograph and measured.
- the longest line segment is the maximum diameter of the single fiber
- the average of the maximum diameters of all selected single fiber cross sections is the maximum diameter of the single fiber of the carbon fiber bundle.
- Example 1 Add 76.5 liters of deionized water to the polymerization kettle overflow port in an aluminum polymerization kettle with a capacity of 80 liters turbine (stirring blade: 240 mm ⁇ (diameter), 2 stages, 4 blades of 55 mm x 57 mm)) Add 0.01 g of ferrous sulfate (Fe 2 SO 4 ⁇ 7H 2 O) and adjust with sulfuric acid so that the pH of the reaction solution becomes 3.0, and keep the temperature in the polymerization vessel at 57 ° C. did.
- ferrous sulfate Fe 2 SO 4 ⁇ 7H 2 O
- AN acrylonitrile
- HEMA 2-hydroxyethyl methacrylate
- AAm acrylamide
- polymer slurry For the polymer slurry, an aqueous solution of a polymerization terminator in which sodium oxalate 0.37 ⁇ 10 ⁇ 2 mol% and sodium bicarbonate 1.78 ⁇ 10 ⁇ 2 mol% was dissolved in deionized water was used. It added so that it might become 5.5-6.0.
- the polymer slurry was dehydrated with an Oliver type continuous filter, and 10 times the amount of deionized exchange water (70 liters) on the mass basis was added to the polymer and dispersed again.
- the polymer slurry after re-dispersion is again dehydrated with an Oliver type continuous filter, pelletized, dried at 80 ° C.
- Polymer A was obtained.
- the composition of the obtained copolymer A was 97.7 mol% AN units, 0.7 mol% HEMA units, 1.6 mol% AAm units, and the specific viscosity was 0.22.
- This copolymer was dissolved in dimethylacetamide (DMAc) to prepare a spinning stock solution having a concentration of 21% by mass.
- the obtained spinning dope had sufficient thermal stability both at 30 ° C. and at 80 ° C. due to the presence of hydroxyalkyl methacrylate and acrylamide in the copolymer.
- spinning was performed by a wet spinning method to obtain a precursor fiber bundle.
- a DMAc aqueous solution having a DMAc concentration of 45 mass% and a temperature of 35 ° C. was used as the coagulation bath.
- the single fiber fineness of the obtained precursor fiber bundle was 2.5 dtex, the number of filaments was 24000, and the roundness of the single fiber cross section was 0.87.
- the precursor fiber bundle was subjected to flameproofing treatment in heated air at 230 ° C. in a hot air circulation type flameproofing furnace, and flameproofing treatment was completed in heated air at 260 ° C.
- the elongation rate was + 2%, and the flameproofing treatment was performed for 70 minutes.
- the density of the obtained flame-resistant fiber was 1.35 g / cm 3 .
- this flame-resistant fiber bundle is subjected to low-temperature heat treatment in a nitrogen atmosphere at a maximum temperature of 660 ° C. and an elongation of 3.0% for 1.5 minutes, and further to a high-temperature heat treatment furnace having a maximum temperature of 1350 ° C. in a nitrogen atmosphere.
- the carbon fiber bundle was obtained by carbonizing for about 1.5 minutes under an elongation of -4.5%.
- the maximum diameter of the cross section of the single fiber of the obtained carbon fiber bundle was 11.0 ⁇ m, and the roundness was 0.86. Furthermore, the strand tensile strength was 4200 MPa, and the strand tensile elastic modulus was as high as 240 GPa. This is because the presence of HEMA units in the precursor fiber keeps the denseness or homogeneity sufficient for the performance of the carbon fiber, and even if the flameproofing treatment is performed at a high temperature in a short time.
- the single fiber cross-sectional shape of the precursor fiber bundle is an empty bean shape with a roundness of 0.87, the distance from the outer periphery of the cross section to the fiber center is shortened, and uniform This is because the flame resistance treatment can be easily performed.
- Example 2 to 16 the copolymer B, respectively, were prepared in the same manner as in Example 1 except that the monomers at the start of polymerization and the supply ratio (molar ratio) were the substances and values shown in Table 1. C, D, E, F, G, H were obtained. The composition and specific viscosity of the obtained copolymer are shown in Table 1.
- HEA means 2-hydroxyethyl acrylate.
- Examples 2 to 6 use copolymers B to F, Examples 7 to 14 use the same copolymer A as Example 1, and Examples 15 and 16 use copolymers G and H, respectively. Except that the number of filaments, the coagulation bath concentration and the coagulation bath temperature shown in Table 1 were changed, a spinning dope was prepared and spun in the same manner as in Example 1 to obtain a precursor fiber bundle. Table 1 shows the stock solution stability of the spinning dope, the single fiber fineness of the precursor fiber bundle, the fiber density, the number of filaments, the coagulation bath concentration, the coagulation bath temperature, and the roundness of the single fiber cross section. The obtained spinning dope had sufficient thermal stability both at 30 ° C. and at 80 ° C. due to the presence of hydroxyalkyl methacrylate or hydroxyalkyl acrylate in the copolymer and acrylamide.
- each of these precursor fiber bundles was subjected to flameproofing treatment in heated air having a temperature shown in Table 1 at a stretching rate and time shown in Table 1 in a hot air circulation type flameproofing furnace.
- the density of each flameproof fiber obtained is shown in Table 1.
- this flameproof fiber bundle was carbonized in the same manner as in Example 1 to obtain a carbon fiber bundle.
- Table 1 shows the maximum diameter of the obtained carbon fiber bundle, the roundness of the cross section of the single fiber, the strand tensile strength, and the strand elastic modulus.
- Comparative Examples 1 to 13 In Comparative Examples 1 to 13, the same method as in Example 1 except that the monomers used in the polymerization and the monomer supply ratio (molar ratio) at the start of the polymerization were changed to the substances and values shown in Table 2. Copolymers I, J, K, L, M, N, O, P and Q were obtained respectively. In Table 2, MAA is methacrylic acid, and IBMA is isobutyl methacrylate. The composition and specific viscosity of the obtained copolymer are shown in Table 2.
- Comparative Examples 1 to 13 were prepared using the same copolymers I to Q as in Example 1 except that the number of filaments, the coagulation bath concentration, and the coagulation bath temperature shown in Table 2 were changed. Spinning was performed to obtain a precursor fiber bundle. However, in Comparative Example 8, the spinnability was poor as compared with other Examples and Comparative Examples, and a precursor fiber bundle could not be obtained. In Comparative Examples 12 and 13, the copolymer was not dissolved in DMAc, and a spinning dope could not be obtained.
- Table 2 shows the single fiber fineness, fiber density, coagulation bath concentration, coagulation bath temperature, number of filaments, and roundness of the single fiber cross section of the precursor fiber bundle.
- the spinning stock solution obtained in Comparative Example 1 was deteriorated in thermal stability at 80 ° C. by MAA contained in Copolymer I.
- the spinning stock solution obtained in Comparative Example 2 was sufficiently stable in heat at 80 ° C. by IBMA contained in Copolymer J, but the heat stability in holding at 30 ° C. was lowered. This is because the AN molar composition contained in the copolymer J is too high in the absence of AAm and unsaturated hydroxyalkyl carboxylate, so that the solubility in the solvent DMAc is not properly maintained, and the undissolved product This is because a large amount exists.
- the spinning stock solution obtained in Comparative Example 3 was improved in thermal stability at 80 ° C. by HEMA contained in the copolymer K, but decreased in thermal stability at 30 ° C.
- the spinning stock solutions obtained in Comparative Examples 5 to 9 were improved in thermal stability in holding at 80 ° C. and holding at 30 ° C. by AAm and IBMA contained in the copolymer M.
- the spinning stock solutions obtained in Comparative Examples 10 to 11 were improved in thermal stability at 80 ° C. and 30 ° C. holding by AAm and HEMA contained in the copolymers N and O, respectively.
- each of these precursor fiber bundles (excluding Comparative Examples 8, 12, and 13) was subjected to flame resistance in a heated air circulation type flameproofing furnace at a temperature shown in Table 2 at an elongation rate and time shown in Table 2. The treatment was performed. The density of each flameproof fiber obtained is shown in Table 2.
- this flameproof fiber bundle was carbonized in the same manner as in Example 1 to obtain a carbon fiber bundle.
- Table 2 shows the maximum diameter of the obtained carbon fiber, the roundness of the cross section of the single fiber, the strand tensile strength, and the strand elastic modulus.
- the strand tensile strength of the carbon fiber bundle obtained in Comparative Example 1 was 3700 MPa, and the strand tensile modulus was 210 GPa, both of which were lower than those of the examples.
- the MAA contained in the copolymer I is different from HEMA and the like, since the carboxy group of MAA is not hydroxyalkylated, the flameproofing reaction proceeds from a low temperature, and the precursor fiber This is because oxygen cannot be diffused into the precursor fiber having a large single fiber fineness due to the low oxygen permeability, and the flameproofing treatment cannot be performed uniformly.
- the strand tensile strength and strand tensile modulus of the carbon fiber bundle obtained in Comparative Example 3 showed high values as in the examples. However, as described above, since the stability of the spinning dope is low, the productivity of the precursor fiber bundle is lower than that in the examples, and as a result, the productivity of the carbon fiber bundle is also reduced.
- Both the strand tensile elastic modulus and strand tensile strength of the carbon fiber bundle obtained in Comparative Example 4 showed a low value as compared with the Examples. This is because the unsaturated carboxylic acid hydroxyalkyl unit does not exist in the copolymer, and acrylamide is different from the unsaturated carboxylic acid hydroxyalkyl, and the flameproofing reaction occurs rapidly at a temperature of 250 ° C. or higher. This is because the formation of a double-section structure is promoted.
- the strand tensile strength of the carbon fiber bundle obtained in Comparative Example 5 was 3500 MPa, and the strand elastic modulus was 220 GPa, both of which were low compared to the Examples. This is because, due to the following points, the flameproofing treatment cannot be performed uniformly, and the formation of a double-section structure is promoted. In other words, acrylamide has a rapid flame-resistant reaction at a temperature of 250 ° C. or higher. Moreover, the unsaturated carboxylic acid ester which does not contain hydroxyalkyl cannot obtain the effect that the flameproofing reaction proceeds slowly from 240 ° C. or higher of the unsaturated carboxylic acid hydroxyalkyl.
- the strand tensile strength of the carbon fiber bundle obtained in Comparative Example 6 was 2200 MPa, and the strand elastic modulus was 180 GPa. Both showed low values compared to the Examples. This is because, due to the following points, the flameproofing treatment cannot be performed uniformly, and the formation of a double-section structure is promoted. In other words, acrylamide has a rapid flame-resistant reaction at a temperature of 250 ° C. or higher. Moreover, the unsaturated carboxylic acid ester which does not contain hydroxyalkyl cannot obtain the effect that the flameproofing reaction proceeds slowly from 240 ° C. or higher of the unsaturated carboxylic acid hydroxyalkyl.
- the coagulation bath conditions for the precursor fiber bundle are a coagulation bath concentration of 65% by mass and a coagulation bath temperature of 55 ° C.
- the roundness of the single fiber cross-sectional shape of the obtained precursor fiber is 0.97 and is a perfect circle. The point to be close.
- the coagulation bath temperature is 55 ° C.
- macrovoids are generated in the fibers as compared with the case where the coagulation bath temperature is 20 to 50 ° C., and the performance of the obtained carbon fiber bundle is deteriorated.
- the strand tensile strength of the carbon fiber bundle obtained in Comparative Example 7 was 2400 MPa, and the strand elastic modulus was 200 GPa, both of which were low compared to the Examples. This is due to the following points.
- acrylamide has a rapid flame-resistant reaction at a temperature of 250 ° C. or higher.
- the unsaturated carboxylic acid ester which does not contain hydroxyalkyl cannot obtain the effect that the flameproofing reaction proceeds slowly from 240 ° C. or higher of the unsaturated carboxylic acid hydroxyalkyl.
- the roundness of the single fiber cross-sectional shape of the obtained precursor fiber bundle is 0.85, which is an empty bean type, but since the coagulation bath temperature is 55 ° C, it is compared with the case where the coagulation bath temperature is 20 to 50 ° C. And a macro void generate
- the strand tensile strength of the carbon fiber bundle obtained in Comparative Example 9 was 3000 MPa, and the strand elastic modulus was 200 GPa, both of which were low compared to the Examples. This is due to the following points.
- acrylamide has a rapid flame-resistant reaction at a temperature of 250 ° C. or higher.
- the unsaturated carboxylic acid ester which does not contain hydroxyalkyl cannot obtain the effect that the flameproofing reaction proceeds slowly from 240 ° C. or higher of the unsaturated carboxylic acid hydroxyalkyl.
- the roundness of the single fiber cross-sectional shape of the obtained precursor fiber bundle is 0.84, which is an empty bean type, but compared with the solidification bath concentration of 30 to 70% by mass and the solidification bath temperature of 20 to 50 ° C.
- the solidification rate is increased, and even when the solidification bath temperature is set to 15 ° C., macrovoids are generated in the fiber, and the performance of the obtained carbon fiber is lowered.
- the strand tensile strength of the carbon fiber obtained in Comparative Example 10 was 3400 MPa, and the strand elastic modulus was 220 GPa, both of which were low compared to the Examples. This is due to the following points. That is, the AN content of the copolymer N is as low as 92.0 mol%. In addition, acrylamide has a rapid flame-resistant reaction at a temperature of 250 ° C. or higher. Furthermore, the content of HEMA is as large as 4.0 mol%, and the flameproofing reaction is too fast, which promotes the formation of a double-section structure.
- the strand tensile strength of the carbon fiber obtained in Comparative Example 11 was 3200 MPa, and the strand elastic modulus was 205 GPa, both of which were low compared to the Examples. This is due to the following points. That is, the AN content of the polymer N is as low as 92.0 mol%. Acrylamide is due to the fact that a flameproofing reaction occurs rapidly at a temperature of 250 ° C. or higher.
- the carbon fiber precursor fiber having a large single fiber fineness and excellent productivity can be obtained uniformly without reducing the productivity in the flameproofing process. It is possible to obtain a high-quality carbon fiber.
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Abstract
Description
本発明のポリアクリロニトリル系共重合体(以下、単に共重合体と称することもある)中のアクリロニトリル単位の含有量は、93.0モル%以上99.4モル%以下である。93.0モル%以上であれば、アクリロニトリル単位の共重合率の低下による炭素繊維性能の低下の影響を受けない。一方、上限の99.4モル%は、後述する共重合成分((メタ)アクリルアミド、分子量が105以下である(メタ)アクリルアミド誘導体および不飽和カルボン酸ヒドロキシアルキル)の必要量から規定されたものである。なお、共重合体中のアクリロニトリル単位の含有量の上限は98.7モル%以下であることが好ましく、下限は、得られる炭素繊維の性能保持の観点から95.0モル%以上であることが好ましい。
ηsp=(η-η0)/5η0・・・式(1)
ηは、共重合体を所定の溶剤に溶解した溶液の粘度であり、η0はこの溶剤の粘度である。溶液の粘度測定は、例えば、共重合体0.5gを100mlの溶剤(例えば、ジメチルホルムアミド)に溶解させ、得られた溶液を、ウベローデ型粘度計を用いて25℃で測定することにより行うことができる。
本発明の共重合体のηspは、0.20以上0.26以下であることが好ましい。0.20以上であれば、得られる炭素繊維の性能低下を容易に抑制することができ、0.26以下であれば、得られる紡糸原液の粘度が低くなり、ゲル化を容易に抑制することが出来る。より具体的には、0.26以下であれば、紡糸原液を調整する際の共重合体の溶剤への溶解性を容易に適正に保つことが出来るため、後述する紡糸原液が30℃程度の低温でゲル化する際に、核となる共重合体の溶け残りが無くなり、ゲル化を容易に抑制することが出来る。
共重合体の製造方法は、特に限定されず、溶液重合、懸濁重合など公知の方法を採用することができる。また、重合開始剤は、特に限定されず、アゾ系化合物、有機過酸化物、また、過硫酸/亜硫酸や塩素酸/亜硫酸のアンモニウム塩などのレドックス触媒を用いることができる。
(1)共重合体を溶剤に溶解して、紡糸原液を調製する工程。
(2)前記紡糸原液を紡糸して、前駆体繊維束を得る工程。
(3)前記前駆体繊維束を、酸化性雰囲気下、220℃以上300℃以下で90分以下、加熱(耐炎化処理)する工程。
(4)工程3より得られた耐炎化繊維束を、不活性ガス中、800℃以上2000℃以下で加熱(炭素化処理)する工程。
上記紡糸原液は、緻密な凝固糸を得るため、また、適正な粘度、流動性を有するために、ある程度以上の共重合体濃度を有することが好ましい。具体的には、紡糸原液における共重合体の濃度は、15質量%以上30質量%以下であることが好ましく、より好ましくは18質量%以上25質量%以下である。
上述の共重合体を溶剤に溶解して、紡糸原液とする。溶剤としては、ジメチルアセトアミド、ジメチルスルホキシド、ジメチルホルムアミドなどの有機溶剤や、塩化亜鉛、チオシアン酸ナトリウムなどの無機化合物の水溶液を用いることができる。前駆体繊維中に金属が含有されず、また、工程が簡略化される点で有機溶剤が好ましく、その中でも凝固糸及び湿熱延伸糸の緻密性が高いという点で、ジメチルアセトアミドを用いることが好ましい。
本発明に用いる炭素繊維前駆体繊維束は、上記共重合体からなる炭素繊維用ポリアクリロニトリル系前駆体繊維で構成される。
前駆体繊維束の単繊維繊度は1.5dtex以上3.0dtex以下であることが好ましい。前駆体繊維束の単繊維繊度が1.5dtex以上であれば、前駆体繊維束の生産性を十分に高くすることが容易に可能となる。一方、前駆体繊維束の単繊維繊度が3.0dtex以下であれば、耐炎化工程において断面二重構造が顕著となることを容易に防ぐことができ、均一な品質の炭素繊維束を安定に生産できる。また、前駆体繊維束の更なる生産性向上と炭素繊維束の品質確保の観点から、単繊維繊度は、1.8dtex以上2.8dtex以下であることがより好ましく、2.0dtex以上2.5dtex以下であることが更に好ましい。
本発明に用いる前駆体繊維束の単繊維の断面形状は、真円度が0.90以下であることが好ましい。また、断面形状は空豆型であることが好ましい。断面形状が真円度0.90以下の空豆型であれば、耐炎化処理時に前駆体繊維束を構成する単繊維内部への酸素の拡散不足を容易に防ぐことができ、十分な耐炎化反応を容易に進行させることができる。その結果、炭素化工程での毛羽が容易に抑えられ、良好な工程通過性を容易に得られ、得られる炭素繊維束の強度や弾性率を容易に適正に維持できる。
真円度=4πS/L2・・・(2)
本発明に用いる炭素繊維前駆体繊維束は、上述のポリアクリロニトリル系共重合体を公知の方法で紡糸することによって製造することができる。以下、紡糸方法を説明する。
炭素繊維前駆体繊維束の交絡度は、繊維束中の1本の単繊維が隣接する他の単繊維と1mの間に何回交絡しているかを示すパラメータである。この交絡度は、フックドロップ法により測定することができる。
<耐炎化処理(工程3)>
得られた前駆体繊維束を、酸化性雰囲気下において、220℃以上300℃以下の温度で90分以下の時間で加熱、即ち耐炎化処理して、耐炎化繊維束とすることができる。なお、カルボン酸ヒドロキシアルキル基の熱分解の観点から、この耐炎化処理中、耐炎化処理温度を少なくとも1度240℃以上の温度とすることが好ましい。本発明において、酸化性雰囲気下は、二酸化窒素、二酸化硫黄、酸素等の酸化性物質を含有する雰囲気下であれば良く、例えば空気中であることができる。なお、酸化性物質とは、酸素を与えることにより物の燃焼を引き起こす物質や、物の燃焼を助長しうる物質を意味する。
耐炎化処理の温度が220℃以上であれば耐炎化反応を暴走させること無く、効率的に耐炎化処理を行うことができる。また、300℃以下であれば前駆体繊維のポリアクリロニトリル骨格を熱分解させることなく耐炎化処理することが容易に可能である。また、処理温度220℃以上300℃以下、かつ処理時間90分以下で、前駆体繊維束を耐炎化処理することにより、得られる耐炎化繊維束の繊維密度を1.35g/cm3以上1.43g/cm3以下まで上げることができる。
耐炎化処理時間は、10分以上90分以下であることが好ましい。耐炎化処理時間が10分以上であれば、前駆体繊維束を構成する単繊維内部への充分な酸素の拡散を容易に行うことが出来る。また、耐炎化処理時間が90分以下であれば、炭素繊維束の製造工程において耐炎化処理工程が生産性を損なう原因となることを容易に防ぐことができ、効率よく炭素繊維束を製造することが可能である。更に、炭素繊維束の性能及び生産性向上の観点から、耐炎化処理時間は、30分以上70分以下がより好ましい。
耐炎化処理によって得られる耐炎化繊維束の密度は、1.35g/cm3以上1.43g/cm3以下であることが好ましい。1.35g/cm3以上であれば、炭素繊維束の収率を低下させること無く炭素繊維束を容易に製造することが可能である。一般的に、耐炎化繊維密度が高いほど得られる炭素繊維束の収率は向上する傾向があるが、炭素繊維の性能は低下する傾向があることが知られており、耐炎化繊維束の密度が1.43g/cm3以下であれば、炭素繊維の性能低下を容易に抑えつつ、得られる炭素繊維束の収率を容易に向上させることが可能である。得られる炭素繊維の性能保持と収率向上の観点から、耐炎化繊維束の密度は、1.38g/cm3以上1.41g/cm3以下がより好ましい。なお、繊維密度は、JIS K7112に基づく密度勾配管法により測定することができる。
<炭素化処理(工程4)>
耐炎化処理後に、得られた耐炎化繊維束を不活性ガス中、800℃以上2000℃以下の温度で加熱、即ち炭素化処理することによって炭素繊維束を製造することができる。上記工程1~4を経て単繊維の最大径が8μm以上20μm以下の炭素繊維束を得ることができる。
炭素繊維束の単繊維の最大径は、単繊維の繊維軸に垂直な断面を走査型電子顕微鏡(SEM)により観察した際の、その断面の外周の2点を結ぶ線分のうちの最も長い線分、即ちその断面の外周上の2点間の距離のうちの最大値とする。
また、単繊維の最大径は9μm以上であることがより好ましく、10μm以上であることがさらに好ましい。これにより、糸束内部における単繊維同士の接触部分を更に少なくすることができ、単繊維同士の摩擦抵抗を容易に減少させることができるため、炭素繊維束の繊維数が多い場合でも広がり性が非常に良好となり、酸素透過性に優れる。
さらに、炭素繊維の強度を低下させない観点から、単繊維の最大径は20μm以下であることが好ましく、15μm以下であることがより好ましく、14μm以下であることがさらに好ましい。これにより、炭素繊維束の単繊維の最大径が太い場合に生じる単位長さあたりの体積増加に比例した欠陥の存在確率の増加を適切な範囲に容易に抑えることができ、炭素繊維の強度が低下することを容易に防ぐことができる。
本発明の製造方法で得られる炭素繊維束の単繊維の断面形状は、炭素繊維束の単繊維の繊維軸に垂直な断面の真円度で表すことができる。真円度は、前駆体繊維束の真円度と同様に式(2)を用いて求めることができる。
また、炭素繊維束の総繊度の上昇によって炭素繊維パッケージ1個あたりの糸長が短くなることによるプリプレグ生産時の生産性の低下を防ぐ観点から、炭素繊維束を構成する単繊維数(フィラメント数)は100000本以下であることが好ましく、80000本以下であることがより好ましく、60000本以下であることがさらに好ましい。
共重合体の組成(各単量体単位の比率(モル%))は、1H-NMR法により、以下のようにして測定した。溶媒としてジメチルスルホキシド-d6溶媒を用い、共重合体を溶解させ、NMR測定装置(日本電子社製、商品名:GSZ-400型)により、積算回数40回、測定温度120℃の条件で測定し、ケミカルシフトの積分比から各単量体単位の比率を求めた。
共重合体0.5gを100mlのジメチルホルムアミド中に分散し、75℃で40分間保持することで、共重合体溶液を得た。この溶液の粘度ηと溶媒(ジメチルホルムアミド)の粘度η0から次式にて算出した。粘度測定はいずれもウベローデ型粘度計で、25℃において行った。
ηsp=(η-η0)/5η0
共重合体42gを158gのジメチルホルムアミド中に分散し、110℃で5分間保持することで得た共重合体溶液を200mLの2つの粘度管にそれぞれ入れ、恒温槽中で、1つの粘度管を30℃に、もう1つの粘度管を80℃に保持した。そして、所定時間ごとに、各共重合体溶液中で鋼球(型番SB-1/4TN:NTN株式会社製)を落とし、落球粘度の経時変化を測定し、ゲル化に要した日数を計測した。なお、この際、30℃で保持した原液(共重合体溶液)の場合は、落球粘度が300Pa・s(3000P)を超えたときに共重合体溶液はゲル化したと判断し、80℃で保持した原液の場合は、落球粘度が30Pa・s(300P)を超えたときに共重合体溶液はゲル化したと判断した。各評価基準を以下に示す。
・30℃保持評価
安定:ゲル化するまでの日数が30日以上のもの、
不安定:ゲル化するまでの日数が30日未満のもの。
・80℃保持評価
安定:ゲル化するまでの日数が50日以上のもの、
不安定:ゲル化するまでの日数が50日未満のもの。
・原液安定性評価
○:30℃及び80℃の保持評価においてどちらも安定である場合、
×:30℃及び80℃の保持評価のどちらか一方でも不安定である場合。
単繊維繊度は、繊維1本の10000m当りの重さを意味し、より具体的には、前駆体繊維束を1mずつ2束とり、各々の質量をフィラメント数(すなわち口金の孔数)で除した後、10000倍し、得られた2つの値の平均値を前駆体繊維束の単繊維繊度とした。
(1)真円度測定用サンプル作製
i)適切な量の前駆体繊維束の繊維軸方向の中央部に木綿糸を半巻きに引っかけ、木綿糸の両端を合わせて、長さ約15mmのポリエチレン細管チューブ(三商(株)、商品名:ヒビキ ポリエチレン細管 No.3)にこの木綿糸を通した。この時、前駆体繊維束はチューブの端部分に止めておいた。なお、使用する前駆体繊維束の量は、上記ポリエチレン細管チューブに前駆体繊維束を入れた際に、動かない程度に詰まった状態となる量が適量である。具体的には、上記ポリエチレン細管チューブに詰めた際に、前駆体繊維の断面形状が圧迫変形しない量であり、緩すぎて撮影時にサンプルが動いて像がブレない量である。
ii)このチューブの端部分に止めておいた前駆体繊維束に静電気防止剤(三井物産プラスチックス(株)製、商品名:スタティサイド)を2秒程度まんべんなく吹き付けた。
iii)チューブに通した木綿糸を引いて静電気防止剤が付着した前駆体繊維束をチューブ内に導入した。
iv)前駆体繊維束が入ったチューブをゴム板上で剃刀を用いて1~3mm程度にカットした。
i)SEM試料台にカーボン両面テープ(日新EM株式会社製、SEM用導電性カーボン両面テープ、幅8mm)を貼りつけ、その上に前記(1)により得られた前駆体繊維束が入ったチューブ(サンプル)を繊維断面が真上になるように精密ピンセットを用いて貼りつけた。
ii)SEM(PHILIPS FEI-XL20(商品名))を用いて観察し、画面上に5個以上の繊維断面が写っている写真を任意に5枚撮影した。
画像解析ソフトウェア(日本ローパー(株)製、商品名:Image-Pro PLUS)を用いて繊維断面の外形をトレースし、周長Lおよび面積Sを計測した。各サンプルについて5枚の写真から任意に20個、ただし、1枚の写真から3個以上の繊維断面を選んで計測し、LおよびSの平均値(Lav1及びSav1)を求め、次式により真円度を算出した。
真円度=(4πSav1)/(Lav1)2
前駆体繊維束及び耐炎化繊維束の繊維密度は、それぞれJIS K7112に基づく密度勾配管法により測定した。
(1)単繊維の最大径測定用サンプル作製
任意の位置で長さ5cmに切断した炭素繊維束をエポキシ樹脂(エポマウント主剤:エポマウント硬化剤=100:9(質量比))に包埋し、任意の位置で2cmに切断して横断面を露出させ、鏡面処理した。
更に、繊維の外形を明瞭にするために、サンプルの横断面を次の方法でエッチング処理した。
・使用装置:日本電子(株)商品名:JP-170 プラズマエッチング装置、
・処理条件
- 雰囲気ガス:Ar/O2=75/25(質量比)、
- プラズマ出力:50W、
- 真空度:約120Pa、
- 処理時間:5min。
前記(1)及び(2)により得られたサンプルの横断面を、SEM(PHILIPS FEI-XL20(商品名))を用いて観察し、画面上に5個以上の繊維断面が写っている写真を任意に5枚撮影した。
各サンプルについて5枚の写真から任意に20個、ただし、1枚の写真から3個以上の単繊維断面を選んで計測し、各単繊維断面の外周の2点を結ぶ線分のうち、最も長い線分をその単繊維の最大径とし、選んだ単繊維断面全ての最大径の平均を、炭素繊維束の単繊維の最大径とした。
画像解析ソフトウェア(日本ローパー(株)製、商品名:Image-Pro PLUS)を用いて繊維断面の外形をトレースし、周長Lおよび面積Sを計測した。各サンプルについて5枚の写真から任意に20個、ただし、1枚の写真から3個以上の繊維断面を選んで計測し、LおよびSの平均値(Lav2及びSav2)を求め、次式により真円度を算出した。
真円度=(4πSav2)/(Lav2)2
炭素繊維束の物性(ストランド強度およびストランド弾性率)は、JIS R 7601に記載の方法に準じて測定した。
容量80リットルのタービン撹拌翼付きアルミニウム製重合釜(攪拌翼:240mmφ(直径)、55mm×57mmの2段4枚羽)に、脱イオン交換水が重合釜オーバーフロー口まで達するよう76.5リットル入れ、硫酸第一鉄(Fe2SO4・7H2O)を0.01g加え、反応液のpHが3.0になるように硫酸を用いて調節し、重合釜内の温度を57℃で保持した。
実施例2~16では、重合開始時の単量体及び、その供給比(モル比)を表1に示す物質及び値とした以外は、実施例1と同様の方法でそれぞれ共重合体B、C、D、E、F、G、Hを得た。得られた共重合体の組成、及び比粘度を表1に示した。なお、表1中のHEAとは、アクリル酸2-ヒドロキシエチルを意味する。
比較例1~13では、重合に用いた単量体、及び重合開始時の単量体の供給比(モル比)を表2に示す物質及び値とした以外は、実施例1と同様の方法でそれぞれ共重合体I、J、K、L、M、N、O、P及びQを得た。尚、表2中のMAAはメタクリル酸、またIBMAはメタクリル酸イソブチルである。得られた共重合体の組成、比粘度を表2に示した。
Claims (8)
- アクリロニトリル単位93.0モル%以上99.4モル%以下と、(メタ)アクリルアミド系単位0.5モル%以上4.0モル%以下と、不飽和カルボン酸ヒドロキシアルキル単位0.1モル%以上3.0モル%以下とからなり、
該(メタ)アクリルアミド系単位が、(メタ)アクリルアミド単位および分子量が105以下である(メタ)アクリルアミド誘導体単位のうちのいずれか一方、または両方であるポリアクリロニトリル系共重合体。 - アクリロニトリル単位93.0モル%以上98.7モル%以下と、(メタ)アクリルアミド系単位1.0モル%以上4.0モル%以下と、不飽和カルボン酸ヒドロキシアルキル単位0.3モル%以上3.0モル%以下とからなり、
該(メタ)アクリルアミド系単位が、(メタ)アクリルアミド単位および分子量が105以下である(メタ)アクリルアミド誘導体単位のうちのいずれか一方、または両方であるポリアクリロニトリル系共重合体。 - 前記不飽和カルボン酸ヒドロキシアルキル単位が、メタクリル酸ヒドロキシアルキル単位およびアクリル酸ヒドロキシアルキル単位のうちのいずれか一方、または両方である請求項1または2に記載のポリアクリロニトリル系共重合体。
- 請求項1~3のいずれか一項に記載のポリアクリロニトリル系共重合体からなる炭素繊維用ポリアクリロニトリル系前駆体繊維。
- 単繊維繊度が1.5dtex以上3.0dtex以下である請求項4に記載の炭素繊維用ポリアクリロニトリル系前駆体繊維。
- 請求項4または5に記載の炭素繊維用ポリアクリロニトリル系前駆体繊維で構成される前駆体繊維束を、酸化性雰囲気下、220℃以上300℃以下の温度で90分以下の時間で加熱して、繊維密度が1.35g/cm3以上1.43g/cm3以下の耐炎化繊維束を得る耐炎化繊維束の製造方法。
- 請求項6に記載の製造方法により得られた耐炎化繊維束を不活性ガス中、800℃以上2000℃以下の温度で加熱して炭素繊維束を得る炭素繊維束の製造方法。
- 請求項4または5に記載の炭素繊維用ポリアクリロニトリル系前駆体繊維で構成される前駆体繊維束を焼成して得られる、単繊維の最大径が8μm以上20μm以下である炭素繊維束:
但し、該単繊維の最大径とは、該単繊維の繊維軸に垂直な断面を走査型電子顕微鏡(SEM)により観察した際の、該断面の外周上の2点間の距離のうちの最大値を意味する。
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EP12817711.0A EP2735575B1 (en) | 2011-07-22 | 2012-07-20 | Polyacrylonitrile-based copolymer, polyacrylonitrile-based precursor fiber for carbon fiber, carbon fiber bundles, process for producing flameproofed fiber bundles, and process for producing carbon fiber bundles |
ES12817711.0T ES2610777T3 (es) | 2011-07-22 | 2012-07-20 | Copolímero a base de poliacrilonitrilo, fibra precursora a base de poliacrilonitrilo para fibra de carbono, haces de fibra de carbono, proceso de producción de haces de fibras resistentes al fuego y proceso de producción de haces de fibras de carbono |
CN201280036083.9A CN103703037B (zh) | 2011-07-22 | 2012-07-20 | 聚丙烯腈系共聚物、碳纤维用丙烯腈系前体纤维、碳纤维束、预氧化纤维束的制造方法、及碳纤维束的制造方法 |
JP2012536624A JP5565467B2 (ja) | 2011-07-22 | 2012-07-20 | ポリアクリロニトリル系共重合体、炭素繊維用ポリアクリロニトリル系前駆体繊維、炭素繊維束、耐炎化繊維束の製造方法、および炭素繊維束の製造方法 |
US14/234,225 US10017881B2 (en) | 2011-07-22 | 2012-07-20 | Polyacrylonitrile-based copolymer, polyacrylonitrile-based precursor fiber for carbon fiber, carbon fiber bundles, process for producing stabilized fiber bundles, and process for producing carbon fiber bundles |
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JP2021046629A (ja) * | 2019-09-19 | 2021-03-25 | 株式会社豊田中央研究所 | 耐炎化繊維、その製造方法、及び炭素繊維の製造方法 |
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